Create find_previous_power_of_two.py

bit_manipulation/find_previous_power_of_two.py

@@ -0,0 +1,30 @@
+def find_previous_power_of_two(number: int) -> int:
+    """
+    Find the largest power of two that is less than or equal to a given integer.
+    https://stackoverflow.com/questions/1322510
+
+    >>> [find_previous_power_of_two(i) for i in range(18)]
+    [0, 1, 2, 2, 4, 4, 4, 4, 8, 8, 8, 8, 8, 8, 8, 8, 16, 16]
+    >>> find_previous_power_of_two(-5)
+    Traceback (most recent call last):
+        ...
+    ValueError: Input must be a non-negative integer
+    >>> find_previous_power_of_two(10.5)
+    Traceback (most recent call last):
+        ...
+    ValueError: Input must be a non-negative integer
+    """
+    if not isinstance(number, int) or number < 0:
+        raise ValueError("Input must be a non-negative integer")
+    if number == 0:
+        return 0
+    power = 1
+    while power <= number:
+        power <<= 1  # Equivalent to multiplying by 2
+    return power >> 1 if number > 1 else 1
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()